Manufacturer recommends 5 m in. before the end of boil. One tab is good for 12 gal., so 1/2 tab is fine for a 5 gal. batch. There's a lot of confusion about this because so many retailers repackage Whirlfloc with inaccurate instructions.

Manufacturer recommends 5 m in. before the end of boil. One tab is good for 12 gal., so 1/2 tab is fine for a 5 gal. batch. There's a lot of confusion about this because so many retailers repackage Whirlfloc with inaccurate instructions.

Wow, you must have some tough Whirfloc! When I add 1/2 tab it dissolves almost instantly.

I add mine at 10 minutes and I crush it with the back of a spoon before adding it. And yes, it does fizz when you add it. I always imagine I'm making some potion and this is the ingredient that goes "poof" and makes the skull and crossbones appear above the kettle like in the Bugs Bunny cartoons.